convert any infix epression/equation to postfix `

hey there guys .... i have to write java code that converts any
infix expression/equation to postfix.... i have been searchiing internet to find some algorithms... but as of now ... i am only able to find algo that might do the simple algebraic conversion but not the trigonometric, log one... can anyone of u please tell me where can i find the algorithm to convert any expression/equation to postfix....